The exons 13, 16, 21 and 23 of cardiacβ-myosin heavy chain (MHC) gene from 32 Chinese patients with hypertrophic cardiomyopathy were analyzed by the polymerase chain reaction and the DNA single strand conformation polymorphism (PCR-SSCP) procedure. The results showed an altered SSCP in exon 13 of one patient. Sequencing analysis revealed that the patient had a G to T transversion in codon 383, resulting in the substitution of Lys by Asn. The missense mutation was also confirmed by Southern blot hybridization with an allele-specific oligonucleotide probe. Because it was found at a residue highly conserved through evolution, this mutation is likely to be the cause of hypertrophic cardiomyopathy in the patient. Because her parents and child were neither clinically nor genetically affected, it was concluded that the mutation in this patient arosede novoand was not passed to her child. This is the first report of a mutant cardiacβ-MHC gene in the Chinese population. Also, it is a novel missense mutation of the cardiacβ-MHC gene.